Symptoms of leaking o-ring at throttle body intake

[Nevets]

Rather than post a long description of an issue I have been having with adjusting the idle speed via BBS and generally rough idling (and occasional stalling)...I ask the following:

What are the symptoms of an air leak upstream from the throttle body, specifically from the o-ring between the throttle body and the plastic intake tube? Also, I don’t suppose anyone has the dimensions of that o-ring, do they?

Thanks for any info.

[Boffin]

Rather than post a long description of an issue I have been having with adjusting the idle speed via BBS and generally rough idling (and occasional stalling)...I ask the following:

What are the symptoms of an air leak upstream from the throttle body, specifically from the o-ring between the throttle body and the plastic intake tube? Also, I don’t suppose anyone has the dimensions of that o-ring, do they?

Thanks for any info.

 

According to the A&S fiche the O-Ring is 52x2mm

 

Andy

[DEF]

Remove the TBs, clean them, reinstall with grease on the O-rings and intake stubs, readjust the TBs and idle air bleeds and you'll be good to go.........

[Nevets]

Yes, thank you both.

I'm wondering if this (TB removal, clean, new o-ring, etc) will help to solve my inability to set a decent idle speed. Bike runs fine otherwise. I did a TBS last weekend, and everything seemed to go fairly well. Although on a previous attempt I was unable to increase the idle speed to 1100 by BBS adjustment. I now notice that the idle speed has once again dropped down to the sub-1000 RPM during idle. Could an air leak in this area cause and idle speed adjustment problem???? I had taken a look at the left o-ring and it seemed to be stretched out, but I did the best to (silicone) grease it and reinstall.

[Mulepick]

What did you clean the TBs with? Brake part cleaner and sometimes carb cleaner can play hell on rubber parts (o-rings). Silicon anywhere in the combustion loop can screw sensors up too. I'd say spring for the new o-rings, clean the silicon off with a intake cleaner, make sure TB and jets are clean and try again.

 

Use a little moly grease to help things pop in.

 

Bob

[DEF]

What did you clean the TBs with? Brake part cleaner and sometimes carb cleaner can play hell on rubber parts (o-rings). Silicon anywhere in the combustion loop can screw sensors up too. I'd say spring for the new o-rings, clean the silicon off with a intake cleaner, make sure TB and jets are clean and try again.

 

Use a little moly grease to help things pop in.

 

Bob

 

A spray with carb cleaner should not harm O-rings used in and around the fuel system. These parts see fuel vapors continually and are not harmed. Most often, dirt, a loose joint, a cut O-ring or some other mechanical issue causes vacuum leaks which promote drivability problems.

 

When reassembling any rubber parts around the induction system, use of silicone grease is acceptable as long as you understand that silicone does poison the CAT system so, use sparingly.

 

Smear a light coating of the grease on O-rings and refit.

 

Also, smear the intake stubs with the same grease. This should cure vacuum leaks as well as keep the rubber parts in good condition.

 

Also, check your air filter. Make sure it is clean and not installed incorrectly or crushed.

 

Finally, when you set the idle vacuum balance (adjust the air bleed screws) check the vacuum readings on your manometer. Record the readings for both sides. Check it a few days later to determine if it has changed. Report back to me with the findings.

[Nevets]

What did you clean the TBs with? Brake part cleaner and sometimes carb cleaner can play hell on rubber parts (o-rings).

Thanks Bob - Carb cleaner used, but o-rings were not exposed to that. They were already goosed out. Bought two new o-rings today.

 

Finally, when you set the idle vacuum balance (adjust the air bleed screws) check the vacuum readings on your manometer. Record the readings for both sides. Check it a few days later to determine if it has changed. Report back to me with the findings.

Thanks DEF (?) - I have no way to take readings, since I have a homemade "water" manometer. Unless I can t-off a hand vac pump i own with guage.... What vac value should I expect to see at that point? Since it may take a while before I can tear into it again, I may PM you at a later date with the results, if that's OK.

[ShovelStrokeEd]

Since your water manometer is used as a differential device rather than measuring actual vacuum, you won't be able to report. Actual vacuum, IIRC, is around 18 cm Hg at idle. You could measure this, I suppose, but you are gonna need a pretty long column as Hg is about 13 times the mass of H2O. You'll need about 2.4 meters or an overall height of 4.8 meters, call it 16 feet. Prolly be pretty bouncy as well.

 

It is useful to check the sync after a couple of days as things do tend to "take a set" and things like engine temp, air temp, relative humidity, phase of the moon, all seem to effect fueling at idle to one degree or another so your spot on setting on Tuesday might actually be just a bit off on Friday.

 

This, BTW, is a really good way to waste a whole bunch of otherwise good riding time. Combination of obsessive/compulsive and anal retentive might never get out of the garage.

[Nevets]

Actual vacuum, IIRC, is around 18 cm Hg at idle.

Ah, good. My hand pump gauge will tell me if it's close. Thanks.

 

This, BTW, is a really good way to waste a whole bunch of otherwise good riding time. Combination of obsessive/compulsive and anal retentive might never get out of the garage.

Don't worry Ed, I'm still getting >500 mi per week even with my obsession, not to mention the time I spend reading these posts...

[RFW]

Rather than post a long description of an issue I have been having with adjusting the idle speed via BBS and generally rough idling (and occasional stalling)...I ask the following:

What are the symptoms of an air leak upstream from the throttle body, specifically from the o-ring between the throttle body and the plastic intake tube? Also, I don’t suppose anyone has the dimensions of that o-ring, do they?

Thanks for any info.

Spray or squirt a little WD40 (or even ---carefully--- gasoline) in places you suspect there is leakage. Even water will often work. Spray or squirt the stuff in one area at a time, and each time listen for a change in idle speed that would result from a temoorary blocking of the leak. This will locate the source of any leak that is there.

 

Bob.